A wide variety of methods for monitoring the operability of a fuel injection system are known from the prior art. The increasingly stringent exhaust gas regulations require ever more precision from the fuel injection systems of internal combustion engines. The requirements placed on the methods for monitoring the operability of fuel injection systems are therefore also becoming more exacting.
DE 198 56 203 C2 discloses a fuel supply system for an internal combustion engine of a motor vehicle whereby fuel is delivered to a pressure accumulator by a pump. Connected to the pressure accumulator are injection valves which supply fuel to the internal combustion engine when activated by a control unit. To monitor the operability of the fuel supply system, the pressure in the pressure accumulator is caused to change by the control unit. The time required to set the pressure change is then measured. The time measured is compared with experimentally determined time values and a fault is deemed to be present if the measured time values do not correspond to the stored time values.
In addition, DE 199 46 506 C1 discloses a method for monitoring malfunctions in the pressure system of a fuel injection system by measuring the pressure change in the pressure system and determining periodic pressure variations. A fault is indicated if the periodicity of the registered pressure measuring signal deviates significantly from the pattern to be expected for fault-free operation of the system in respect of the amplitude and/or homogeneity of the pressure variations.